WELLINGTON - New Zealand's warning system for volcanoes rates them on a scale of zero to five, with zero indicating no activity, while ratings from three to five mean that an eruption is taking place.
In the weeks before the eruption of the White Island volcano, New Zealand volcano monitoring service GeoNet (GNS) raised its alert level to level 2, which means that low level volcanic activity is taking place.
According to GNS, the system has been in place since 2014 and was created based on extensive consultation with stakeholders.
The warning system, however, doesn't explain what the likely hazards are, nor do they tell visitors how to act. They also don't carry any legal weight, so any precautionary actions to be taken are left to the discretion of those visiting the volcano.
What's more, volcanoes like White Island can erupt even if they are rated at level one on the warning system. GNS volcanologist Graham Leonard told CNN that GNS staff visited the island in the weeks leading up to the eruption.
To visit White Island, which has been privately owned by the same family for 80 years, tour operators and individual travellers need to get permission.
On Monday (Dec 9), the day of the eruption, White Island Tours - a company based in the nearby beach town of Whakatane - took 38 tourists to the island when the alert level was two. According to White Island Tours chairman Paul Quinn, visitors could be taken to the island even during a level two alert, under the company's internal guidelines.
"There was nothing that signalled there was going to be an eruption," he said.
It is pertinent to note that White Island Tours and other operators organising trips to the volcano still have to comply with the country's health and safety standards, which are set by government regulator Worksafe.
Worksafe did not reply to CNN's query on whether the visit to the island during a level two alert complied with its health and safety standards. However, it said in a statement that it had opened a health and safety investigation into the loss of life due to the eruption.
Separately, the police said they were investigating the deaths and injuries on behalf of the coroner, adding that it was too early to confirm whether there would also be a criminal investigation.